I want to make sure I understand the use of the term "variable". If my son is trying to determine if you are more likely to roll a sum of at least 18 with 3 ten-sided dice or 5 six-sided dice, is this only one variable? He has a project due and he is not allowed to have more than one variable.

There are two types of variables. Independent and dependent variables.- Independent variables are those you change throughout the experiment and COULD affect change on the outcome. I say COULD, because the may not. You won't know this until you run your experiment.- Dependent variables are your measurements of outcome affected by changes in the independent variable(s).

From these definitions, can your son determine his dependent and independent variables? If not, feel free to write back what you think they are and why, and we can chat more.